Conventionally, there has been implemented a task of bringing a probe into contact with a pad contained in a wiring pattern formed on a semiconductor substrate to inspect electrical characteristics of the wiring pattern, which task is referred to as “probing by a prober”. In such a probing process, a task is conducted for correcting a contact position of the probe on the pad, which task is called “PTPA (Probe-To-Pad Alignment)” or “APTPA (Automatic Probe-To-Pad Alignment)”.
For example, Japanese Patent Laid-open Publication No. H6-318622 (Reference 1) discloses a technique of bringing a probe into contact with a pad on a so-called dummy substrate, then picking up an image of a region inclusive of the pad to detect a contact mark of the probe (i.e., a probe mark) on the pad, and correcting a contact position of the probe with respect to the substrate pad, namely, a test object, based on the result of detection of the probe mark.
Further, Japanese Patent Laid-open Publication No. 2004-79733 (Reference 2) proposes a technique of adjusting a contact position of a probe with respect to a pad, by virtue of picking up an image of a region inclusive of the pad while irradiating a spot light on a substrate pad to form a focal point at the same height as a leading end of the probe in a probing process, and then detecting an on-pad position of the irradiated light.
In the meantime, a probe mark inspection (referred to as “PMI”) is also carried out by capturing a multiple tone image of a region inclusive of a pad in the probed substrate. In this way, it is confirmed whether the probing has been properly conducted or not.
Further, Japanese Patent Laid-open Publication No. H7-29946 (Reference 3) discloses a technique of adjusting an overdrive amount at a time when a probe is brought into contact with a next inspected pad, by capturing an image of a pad-inclusive region from a probed substrate and measuring the length of a probe mark on the pad.
By the way, in case of employing the techniques taught in References 1 and 2 to conduct the correction of a probe contact position with respect to a pad, it is inevitable either to detect a probe mark on a pad of a dummy substrate or to detect an irradiated position of a spot light on a pad, which leads to a prolonged probing time.
Moreover, in the event that a probing is conducted several times for a single pad, probe marks are left on the pad in plural numbers. This means that no deviation in a probe contact position can be detected merely by capturing an image that contains the pad. Particularly, if the latest probe mark overlaps with other probe marks (whether intentional or not), it becomes extremely difficult to detect a deviation.